Image sensors have become ubiquitous. They are widely used in digital still cameras, cellular phones, security cameras, medical, automobile, and other applications. The technology used to manufacture image sensors, and in particular CMOS image sensors, has continued to advance at great pace. For example, the demands of higher resolution and lower power consumption have encouraged the further miniaturization and integration of the image sensor. Thus, the number of pixels in the pixel array of the image sensor has significantly increased.
For example, five megapixel CMOS sensors are currently being manufactured today. This large array of pixels represents a significant amount of data to be gathered and read out. Additionally, the speed of acquisition and readout of the data is becoming an issue. The smaller and more complex pixels presents difficulties in routing all of the signal and power lines into and out of the pixel array, yet maintaining low cost and high performance. Complicating matters further, the “stack height” of the image sensor is also a factor. Image sensors benefit from low stack height which improves optical crosstalk and the ability of a microlens to effectively focus light onto the pixel-sensing area.
Thus, a method and structure for improving routing into and out of each individual pixel without increasing the stack height is desirable. Further, it would be advantageous if this structure could also be used in the peripheral regions (those regions of the image sensor outside of the pixel array) to improve speed, performance and size of the circuits formed in the peripheral regions.